@article{IM2_1985_25_2_a3,
     author = {A. G. Eliseev},
     title = {Singular perturbation theory for systems of differential equations in the case of multiple spectrum of the limit {operator.~I,~II}},
     journal = {Izvestiya. Mathematics },
     pages = {315--357},
     publisher = {mathdoc},
     volume = {25},
     number = {2},
     year = {1985},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1985_25_2_a3/}
}